How to disable/enable a plugin at a specific time

You can use deactivate_plugins() function to deactivate a plugin

if ( ! wp_next_scheduled( 'deactivate_plugin_conditional_hook' ) ) {
  wp_schedule_event( time(), 'twicedaily', 'deactivate_plugin_conditional_hook' );
}

add_action( 'deactivate_plugin_conditional_hook', 'deactivate_plugin_conditional_2345678999343434' );

function deactivate_plugin_conditional_2345678999343434() {
$plugin_path="plugin-folder/plugin-name.php";
    if ( is_plugin_active($plugin_path) ) {
    deactivate_plugins($plugin_path);    
    }
}

You can set custom event see here https://codex.wordpress.org/Function_Reference/wp_schedule_event

Note: this is not tested code